This invention relates to a construction of the gear train for a timepiece, at least one wheel thereof being coaxially and freely mounted on a common axle with other wheels.
In a conventional type of gear train driven by a stepping motor having a two-poled rotor, said rotor is driven 1/2 rotation per one second and further driven 30 rotations per one minute. On the other hand, a second hand axis (a fourth gear wheel) is driven 1 rotation per one minute so that the rotary speed ratio between a rotor axis and said second hand axis is set at 1 : 30. Therefore, the gear ratio for coupling said rotor axis and said second axis using one step coupling of a gear system must be set at 30 : 1.
In general, a realization of the gear ratio of 30 : 1 using said one step coupling is very difficult in conventional engineering.
Accordingly, the other gear wheel (an intermediate coupling gear) for a gear reduction must be mounted on a separate axle between said second hand axle and rotor axle in view of the manufacturing of a gear wheel. However, it is very difficult to construct a small watch in view of the large spaces needed to accommodate the battery, a crystal quartz block and a circuit block.
Therefore, it will be lacking of the commodity value as a watch for women and men.